ELECTROMAGNETIC RESPONSE OF TWO‐DIMENSIONAL INHOMOGENEITIES IN A DISSIPATIVE HALF‐SPACE FOR TURAM INTERPRETATION

Abstract

An integral equation technique based on the integral formulation of the electric field of a harmonically excited line‐source in the presence of a two‐dimensional scattering in‐homogeneity is outlined. In this treatment the inhomogeneity is assumed to have an arbitrary cross‐sectional shape and to be located in a layered, dissipative half‐space. The scattering responses in terms of the horizontal and the vertical magnetic field components observed on the ground surface are studied for a variety of geologic models involving overburden layers, vertical or inclined veins and multiple inhomogeneities. The horizontal component of the total magnetic field appears to be the most diagnostic response parameter. A thin vein shaped target with a cross sectional area of 0.05 δ2× 0.50 δ2 (δ2 being the skin‐depth in the lower half‐space) located 0.50 δ2 away from the line‐source and under a highly conductive overburden layer (σ1/σ2= 300) of thickness 0.02 δ2 is easily detected with a moderate resolution. The scattering responses are also sensitive to changes in depths of burial, inclination and conductivity contrast with the surrounding half‐space of the target inhomogeneity. An interpretation scheme as well as a number of characteristic detectability parameters are developed for the conventional Turam method used in mineral exploration. Copyright © 1973, Wiley Blackwell. All rights reserved